ASK TOM WHY

Nevada!?!? I thought Arizona was the driest state with 7.5 inches of rain annually.

-- Elise White Pearce

Dear Elise,

You are referring to our statement on July 21 that "Nevada, with a scant 9 inches [of rain] annually, is the driest [state]."

The annual total that you suggested for Arizona -- 7.5 inches -- is representative only of central Arizona. Other areas of the Grand Canyon State, especially the higher elevations of the north, receive up to 22 inches. The state as a whole gets 14 inches.

Nevada lies in the "rain shadow" of the Sierra Nevada Mountains to its west, and it is sheltered from precipitation accompanying storms from the Pacific Ocean.

In addition, Arizona experiences a summer monsoon when thunderstorm-triggering moisture from the Gulf of California, just to the south, works its way across the state.